1. Field of the Invention
The present invention relates to indirectly controlled exchanges, and more particularly to circuit arrangements for such exchanges in which fault signals are generated and the operating status of the test points in the exchange are determined, stored and processed with the test data for analysis by output apparatus.
2. Description of the Prior Art
As is known, control devices of exchanges, in particular telephone exchanges, are subject to particularly high requirements. The exchanges are indirectly controlled exchanges which have central control devices which must handle the switching operation and other, more extensive, processes. In modern exchanges, central control devices of this type have various sub-devices, e.g. working registers, calculators, a memory in which program commands are stored and which can also serve as a working memory. A particularly high requirement to which such exchanges are subject resides in the fact that associated control devices must carry out a real-time operation which, as far as possible, must not be impermissibly disturbed by interruptions due to reported faults. Therefore, in control devices of this kind it is necessary to take measures for rapid determination of faults in order that such faults may be eliminated.
Various methods are already known in the art for establishing faults in control devices of this kind. Of particular interest is a circuit arrangement in which, in the case of a fault, test data are stored. In this connection, one may refer to the German Pat. No. 1,108,747. This circuit arrangement is also provided for an indirectly controlled exchange, in particular a telephone exchange. This exchange also has central devices. On the occurrence of a fault signal, the operating states prevailing in the exchange are stored by means of test data. The test data indicate the electrical states prevailing at specific test points and are input into a memory, for which purpose the operating state prevailing in the exchange is temporarily stored. Test data of this kind can, on the one hand, be extremely extensive, and, on the other hand, can indicate very special electrical states which, if at all, can only be checked for accuracy and reliability with a high expense. Particular difficulties occur if the test data has been produced by a sporadic fault. In such a case, it is not possible to localize the fault with the aid of a test program, as it is not likely that it will occur during the course of the test program.